This invention relates to solenoid fuel drain valves, in particular, although not exclusively, to solenoid drain valves for use in automotive fuel systems.
Fuel systems, generally comprise a fuel filter to remove water and other contaminates from the fuel. The fuel filter is generally part of a closed system. It is preferable to periodically remove the water and other contaminates from the fuel filter.
This may be achieved using a manual fuel drain valve. The operator of a manual fuel drain valve periodically releases the water and other contaminates by rotating the drain valve. Water and contaminates can be released from the fuel filter by draining through a first hole in the valve as air enters the fuel filter through a further hole in the valve.
A manual fuel drain valve is inconvenient because the fuel filter is often positioned in an awkward location in an automotive engine and is not easily accessible.
As an alternative, solenoid activated fuel drain valves have been developed. Solenoid fuel drain valves are electrically operated. A solenoid fuel drain valve may be controlled automatically by, for example, an engine control system, or mechanically by, for example, activation of a switch by an operator.
To operate a solenoid fuel drain valve, a solenoid coil is activated to cause a plunger to be pulled from a closed position to an open position. In order to allow water and other contaminates to be released from the fuel filter the fuel system must be pressurised. In some arrangements, residual pressure from the fuel system provides enough pressure for the water and other contaminates to flow through the drain valve when opened by the solenoid. In other arrangements, it may be possible to mount the fuel filter below the fuel tank to create the required pressure difference. Otherwise, a means of pressuring the fuel system must be provided in addition to the solenoid fuel drain valve, in order to provide for drainage of the water and other contaminates through the valve when the valve in opened by the solenoid.
In automotive engines in particular, it is not always possible to arrange the fuel filter below the fuel tank, and provision of additional pressurisation means adds undesirable expense to the manufacturing and maintenance costs.